Barrier coated electrophotographic sheet suitable for liquid development

ABSTRACT

An electrophotographic reproduction process and copy sheet therefor for development of a latent electrostatic image on the copy sheet by a liquid developer wherein the copy sheet comprises a conductive base sheet having a thin barrier coating on each side thereof, the coating comprising a highly dielectric insulating material and a conductor material which is either a polymeric quaternary ammonium halide or an ammonium salt of an alkyl aryl sulfonate, and one side having a second coating thereon comprising a thin insulating coating or a photoconductor coating for receiving an electrostatic image.

United States Patent Rowe [451 Mar. 28, 1972 [54] BARRIER COATEDELECTROPHOTOGRAPHIC SHEET SUITABLE FOR LIQUID DEVELOPMENT [72] Inventor:Clifton B. Rowe, Chicago, 111.

[73] Assignee: A. B. Dick Company, Chicago, 111.

[22] Filed: Mar. 16, 1970 [21] Appl. No.: 19,954

3,479,215 11/1969 Cavagna et al. ..1 17/201 3,486,936 12/ 1969 Cahill..117/224 3,155,503 11/1964 Cassiers et a1.. ..96/1 3,293,115 12/1966Lucken ..162/184 3,110,621 11/1963 Doggett etal.. ..117/2l8 3,248,2794/1966 Geyer ..162/138 3,385,730 5/1968 Relph ..1 17/201 3,116,14712/1963 Uber ..96/1

Primary Examiner-Donald Levy Assistant Examiner-John C. Cooper, 111Attorney-McDougall, Hersh & Scott [57] ABSTRACT An electrophotographicreproduction process and copy sheet therefor for development of a latentelectrostatic image on the copy sheet by a liquid developer wherein thecopy sheet comprises a conductive base sheet having a thin barriercoating on each side thereof, the coating comprising a highly dielectricinsulating material and a conductor material which is either a polymericquaternary ammonium halide or an ammonium salt of an alkyl arylsulfonate, and one side having a second coating thereon comprising athin insulating coating or a photoconductor coating for receiving anelectrostatic image.

23 Claims, 3 Drawing Figures PATENTEnmza I972 3, 652,268

N VfN 702 Clzfton 5. Rowe 5% aiiks BARRIER COATED ELECTROPHOTOGRAPHICSHEET SUITABLE FOR LIQUID DEVELOPMENT This invention relates to anelectrostatic copy process and more particularly to copy paper for usein electrostatic reproduction processes, such as the Videograph processof the A. B. Dick Company, or the Electrofax process.

in the Borden et al. U.S. Pat. No. 2,879,422, Crews U.S. Pat. No.2,928,973, Borden U.S. Pat. No. 2,978,607, Barnes et al. U.S. Pat. No.2,996,573, Evans et al. U.S. Pat. No. 3,017,625, and Relph et al. U.S.Pat. No. 3,075,859, description is made of the process identified as theVideograph process. Briefly described, use is made of a cathode ray tubewhich directs a video signal onto an array of conductive wires extendingthrough the face of the tube. The wires discharge onto a groundedwriting medium having a dielectric insulating coating, duringadvancement of the writing medium adjacent the face of the tube, to forma latent electrostatic image which is retained on the dielectricinsulating coating until developed by toner particles in accordance withconventional electrostatic copy technique.

A writing medium suitable for use in the practice of the Videograph copyprocess is described in the aforementioned patent of Relph et al. inwhich the writing medium comprises a paper base sheet having. acontinuous dielectric insulating coating on one surface and in which thepaper base sheet is rendered more conductive as by modification toinclude a humectant and/or a water soluble, water stable, ionizablemetal salt uniformly distributed throughout the base sheet.

The paper base sheet itself is sufficiently conductive but theconductivity can be stabilized against change in response to change inhumidity and otherwise rendered more conductive by the modificationdescribed or by other techniques, such as impregnation to includeconductive carbon in the base sheet or by wetting the base sheet withaqueous or other liquid electrolyte immediately prior to receiving theelectrostatic discharge from the cathode ray tube.

A writing medium of the type described has been found to be suitable foruse in the development of copy with dry toners wherein the dry tonerparticles are dusted, cascaded, or otherwise applied over the surfacecontaining the latent electrostatic image whereby toner particles areretained by the imaged portions for visual development while thenon-imaged portions remain free of toner particles. Thus, clean andclear copy is produced without noticeable background color.

When the latent electrostatic image is developed by means of a liquiddeveloper, such as described in the Metcalfe et al. U.S. Pat. No.2,907,674, or the Mayer U.S. Pat. Nos. 2,891,81 l and 2,877,l33, aconsiderable amount of discoloration occurs in the copy sheets. It isbelieved that this stems, at least in part, from the exposure of theback side of the paper base sheet to the liquid developer whereby thepaper base sheet becomes impregnated with developer during developmentof the latent electrostatic image. Such liquid developer is retained inthe paper base sheet whereby toner particles remain to effect thedescribed discolorations.

ln copending application, Ser. No. 859,949, filed Sept. 22, 1969, andentitled Copy Process for Electrostatic Printing, description is made ofan electrostatic reproduction process using a copy sheet which comprisesa conductive base sheet having a thin continuous insulating coating onone side for receiving the electrostatic image and which is preferablytreated on the other side or back side with a humectant to increase theelectrical conductivity of the base sheet. Thereafter the back side isfurther treated to provide a thin, continuous coating thereon whichserves as a barrier to provent absorption of developer liquid and whichhas an electrical resistivity of not more than 1.0 X ohms per squarecentimeter. The copy sheet described in the aforementioned copendingapplication represents a significant improvement over copy sheetsheretofore known in that it virtually eliminates discoloration of thecopy sheets during development thereof by absorption of developerliquid. However, the copy sheet is expensive to prepare in that it isnecessary to provide three separate treatments for its preparation.

It is accordingly an object of the present invention to provide anelectrostatic reproduction process and copy sheet therefor wherein thecopy sheet is coated on both sides with a conductive barrier coatingcomposition and is thereafter top coated to provide a dielectricinsulating coating or a photoconductive coating which receives thelatent electrostatic image.

It is a related object of the present invention to provide a process ofthe type described wherein use is made of a copy sheet which retains thedesired characteristics of a highly dielectric insulating coating or aphotoconductive insulating layer on an electrically conductive basesheet for receiving and retaining the electrostatic image; in which drycopy can be produced within a short period of time after development ofthe latent image; and, in which good clean copy can be produced byelectrostatic techniques.

These and other objects and advantages of the invention will appearhereinafter, and, for purposes of illustration, but not of limitation,an embodiment of the invention is shown in the accompanying drawingwherein:

FIG. 1 is a sectional view of a copy sheet embodying the concepts of theinvention;

FIG. 2 is a schematic view of the visual development of the latentelectrostatic image on a copy sheet of the type shown in FIG. 1', and,

FIG. 3 is a sectional view similar to that of FIG. 1 after developmentof the latent electrostatic image.

The concepts of the present invention reside in an electrostaticreproduction process and copy sheet for use in same wherein the copysheet comprises a conductive base sheet which has been coated on bothsides thereof with a composition comprising a material which is abarrier to the penetration of liquid and a water soluble conductormaterial selected from the group consisting of a polymeric quaternaryammonium halide and an ammonium salt of an alkyl aryl sulfonate toprovide a thin, continuous conductive barrier coating on the copy sheet.Thereafter, one side of the treated base sheet is provided with aconventional coating adapted to receive the electrostatic image. Forexample, for use in the Videograph process, the copy sheet is providedwith a dielectric insulating coating which operates to retain the latentelectrostatic image formed thereon. For use in the Electrofax process,the copy sheet is provided with a photoconductive layer or coating whichforms a latent electrostatic image in response to a corona dischargefollowed by exposure to light modulated by an image.

It has been found that the conductive barrier coating on the conductivebase sheet imparts the desired conductivity to the base sheet paper, andat the same time prevents absorption of the liquid developer compositionby the base sheet to thereby provide good clean copy on development ofthe latent electrostatic image.

A wide variety of materials may be used to provide the barrier coatingin accordance with the invention, such as polyvinyl acetate,acid-modified polyvinyl acetate such as crotonic acid-modified polyvinylacetate, polyethylene, wax, unmodified or oil-modified alkyd resins,nitrocellulose, ethyl cellulose, carboxymethyl cellulose, celluloseacetate, shellac, polyester resins, organo silicon resins, polyvinylchloride, copolymers of butadiene and styrene, polyvinyl butyral,acrylic acid polymers and copolymers as well as a variety of otherdielectric materials known to those skilled in the art. However, it isgenerally preferred in the present invention to make use of polyvinylalcohol since it appears to be more compatible with the conductormaterial, and is easier to work with owing to its solubility in water.

The water soluble conductor materials useful in accordance with theinvention include polymeric quaternary ammonium halides, andparticularly the chlorides, and ammonium salts of alkyl aryl sulfonates.Preferred polymeric ammonium halides are the polydialkyl divinyl andpolydialkyl diallyl ammonium halides wherein the alkyl group containsone to four carbon atoms, such as methyl, ethyl, propyl, etc.Particularly suitable is polydirnethyl diallyl ammonium chloride whichis commercially available under the trademark Calgon 261.

A wide variety of ammonium alkyl aryl sulfonates are similarly suitablefor use in the present invention, and particularly those where the alkylgroup contains 1-20 carbon atoms and the aryl group is either a benzeneor naphthalene group. Particularly preferred is RP 505 from Monsantowhich is the ammonium salt of an alkylated benzene sulfonate.

It is possible, and frequently preferred, to include, in the coatingvarious filler and extender materials which operate to increase thestability of the coating and the increase of its conductivity. For thispurpose, use can be made of vinyl acetate emulsion, such as vinylacetate emulsion 25-1025 from National Starch, and/or hydrated ammoniumsilicates.

The relative proportions of the dielectric material, the conductivematerial and the filler and/or extender, when present, in thecomposition for treating the conductive base layer are not critical. Itis generally sufficient that the barrier material and the conductivematerial each be present in an amount within 0.1 and 20 percent byweight, and that the vinyl acetate emulsion, when present, constitutebetween 1 and 25 percent by weight of the composition. The hydratedammonium silicates preferably constitute between 1 and 15 percent byweight.

Having described the basic concept of the invention, reference is nowmade to the following examples, which are provided by way ofillustration, and not by way of limitation of specific embodiments ofthe invention. All parts given are parts by weight.

EXAMPLE 1 parts Ammonium alkyl benzene sulfonate' (RP 505-Monsanto) 10parts 6% solution of polyvinyl alcohol in water (Evanol 72$ 1 -DuPont)250 parts Water The foregoing composition is used to impregnate bothsides of a paper base sheet in dry coating weights of 2-3 pounds per3,000 square feet of paper on each side. The resulting paper has aresistivity of 4 X 10 ohm-cm. at 90 F. and 10 percent relative humidity,and 8 X 10 ohm-cm. 72 F. and 50 percen relative humidity.

The foregoing composition is applied to both sides of a base sheet bymeans of a blade to provide a coating of 2 to 4 lbs. per 3,000 squarefeet on each side. Tests at 72 F. and 50 percent relative humidity andrevealed a surface resistance of 10 ohms-cm and 90 F. and 10 percentrelative humidity.

EXAMPLE 3 1.100 parts 12% solution of polyvinyl alcohol in water 295parts Ammonium alkyl benzene sultonate(RP 505-Monsanto) 930 parts 25%hydratedammoniumsilicate I in water 480 parts Vinyl acetate emulsion1.000 parts Water The foregoing composition may be applied to a basesheet by conventional procedure to apply a uniform coating across thebase sheet in a coating weight of 2-14 lbs. per 3,000 square feet ofsurface area per side, followed by air drying or drying at an elevatedtemperature within the range of to 250 F.

A sectional view of a base sheet treated in accordance with the presentinvention is shown in FIG. 1, and comprises a conductive base sheet 10formed of conventional paper having a thin coating 12 and 14 on eachside of the base sheet comprising one of the compositions of Examplesl-3. The coating 12 and 14 may be applied in a conventional manner, andcontain between 5-50 percent of the barrier material, 1.0-75 percent ofthe conductive material, and, when present, 15-40 percent of thehydrated ammonium silicate and up to 40 percent by weight of vinylacetate plus emulsifier.

As shown in FIG. 1, the copy sheet also includes a second coating on onesurface thereof wherein the section coating 16 comprises either a thininsulating coating or a photoconductor coating for receiving anelectrostatic image. For example, when the copy sheet is to be used inthe Videograph process, the treated base sheet having the thinconductive barrier coatings l2 and 14 thereon is provided with a secondcoating 16 on one surface thereof wherein the coating 16 is formed of ahigh dielectric insulating material which operates to retain the latentelectrostatic image on the copy sheet. For this purpose, use can be madeof polyvinyl acetate or a polyvinyl acetate acidic polymer, such aspolyvinyl acetate with crotonic acid.

As described in the aforementioned patent of Relph et al., thedielectric insulating coating 16 can also be formulated of polyethylene,wax, unmodified or oil-modified alkyd resin, nitrocellulose,ethylcellulose, cellulose acetate, shellac, polyester resin,organo-silicon resin, polyvinyl chloride, butadiene-styrene copolymer,polyvinyl butyral, acrylic acid polymer or copolymer. Such highdielectric insulating materials may be applied onto the base sheet fromsolvent solution or from an aqueous dispersion in coating weights offrom 2 to 4 pounds per 3,000 square feet of surface area. Instead ofproviding the dielectric insulating layer 16 by coating technique, afilm of the dielectric insulating material can be laminated onto the oneside of the paper base sheet.

The following examples are provided by way of illustration of thepreparation of a high insulating layer on a base sheet which has beentreated on both sides with one of the compositions of Examples 1-3.

EXAMPLE 4 36.5% by weight Oil-modified alkyl resin (50% solids) (Aroplaz7424 of Archer-Daniels-Midland 12.01% by weight Resin(Piccopalel00-Pennsylvania Industrial Chemical Company) 21.0% by weight Xylene30.5% by weight Barium sulphate Application of the coating compositioncan be made onto the paper base sheet by conventional coating procedureto apply a uniformlayer across the base sheet in a coating weight of2-14 pounds per 3,000 square feet of surface area, followed by airdrying or drying at an elevated temperature within the range of l25-250F.

For use in the Electrofax process, the base sheet is treated inaccordance with the concept of the present invention and thereafterprovided with a thin coating of an inorganic or organic photoconductor,which is preferably admixed with an insulating material of the typedescribed above which operates as a binder for the photoconductormaterial. Such binders preferably have a resistivity greater than ohmcm. In addition to the foregoing materials, use can also be made ofother resinous binders, such as a Union Carbide resin, identified asVMCH, which is formulated of 86 percent by weight vinyl chloride, 13percent by weight vinyl acetate and 1 percent by weight maleic acid,polystyrene, acrylate and methacrylate ester polymers, Acryloid A10 andchlorinated rubber, such as Parlon.

A wide variety of photoconductors may be used in preparing thephotoconductive layer. For example, use can be made of conventional zincoxide photoconductors as described in the Grieg U.S. Pat. No. 3,052,539,or in the Middleton U.S. Pat. No. 3,121,006. Use can also be made oforganic photoconductors, including polymers of N-vinyl carbazole or thedimer of an N-vinyl carbazole as described in copending application,Ser. No. 612,432, with or without various sensitizers.

The following examples are provided by way of illustration of thepreparation of a photoconductive layer on a base sheet which has beenpreferably treated with one of the composi- The foregoing compositionsare applied to the treated base sheet so as to provide a coating weightof within the range of 0.25- pounds per 3,000 square feet of surfacearea.

A copy sheet prepared in accordance with the concept of the presentinvention can be completely immersed in the liquid developer fordevelopment of the latent electrostatic image without discoloration ofthe back side of the copy sheet. As shown in FIG. 2, the copy sheet 15which has been treated in accordance with the present invention isadvanced over roller 18 into a bath of the liquid developing compositionwhereby toner particles are retained by the electrostatically imagedportions of sheet 15. The retained diluents on the copy sheet arerapidly eliminated by advancing the developed copy sheet through a hotzone 22, to which heat may be supplied by conventional means, such asthe infra-red lamps 24, or by conventional electrical resistivityheaters or a circulating hot air stream.

The resulting developed copy sheet is shown in FIG. 3 wherein thecoating 16 on one side of the conductive base sheet 10 contains thevisual image in the form of toner particles 26 which are attracted tothe coating 16 in the areas corresponding to the areas of the coating 16containing the latent electrostatic image.

It will be apparent from the foregoing that I have provided a new andimproved electrostatic copy process and copy sheet for use therein whichcan be employed in either the Videograph process or the Electrofaxprocess to provide good clean copy without discoloration of the copysheet caused by absorption of the liquid developer in the copy sheet.

It will be understood that various changes and modifications may be madein the details of formulation, application and use without departingfrom the spirit of the invention, especially as defined in the followingclaims.

Iclaim:

1. An electrophotographic reproduction sheet for development of a latentelectrostatic image by a liquid developer comprising a conductive basesheet having a thin continuous conductive barrier coating on each sidethereof, said coating comprising a resinous material which is a barrierto the penetration of liquid and a conductor material selected from thegroup consisting of a polymeric quaternary ammonium halide selected fromthe group consisting of polydialkyl divinyl ammonium halides andpolydialkyl diallyl ammonium halides and an ammonium salt of an alkylaryl sulfonate, and a second coating on one side of said base sheet,said second coating comprising a material adapted to receive anelectrostatic image.

2. A reproduction sheet as defined in claim 1 wherein said barriermaterial is polyvinyl alcohol.

3. A reproduction sheet as defined in claim 1 wherein said conductormaterial is polydimethyl diallyl ammonium chloride.

4. A reproduction sheetas defined in claim 1 wherein the conductormaterial is an ammonium salt of an alkyl aryl sulfonate in which thearyl group is selected from a group consisting of a benzene group and anaphthalene group and contains one or more alkyl groups having 1-20carbon atoms.

5. A reproduction sheet as defined in claim 1 wherein coating contains5-50 percent by weight of said barrier material and 1-75 percent byweight of said conductor material.

6. A reproduction sheet as defined in claim 1 wherein said barriercoating includes .vinyl acetate.

7. A reproduction sheet as defined in claim 6 wherein said vinyl acetateis present in an amount up to 40 percent by weight of said coating.

8. A reproduction sheet as defined in claim 1 wherein said barriercoating includes a hydrated ammonium silicate.

9. A reproduction sheet as defined in claim 8 wherein said ammoniumsilicate is present in an amount within the range of 15-40 percent byweight of said coating.

10. A reproduction sheet as defined in claim 1 wherein said barriercoating is present in a dry coating weight of 2-14 pounds per 3,000square feet of surface area.

11. A reproduction sheet as defined in claim 1 wherein said material forreceiving the electrostatic image is selected from the group consistingof a high insulating material and a photoconductive material.

12. An electrostatic copy process in which use is made of a liquiddeveloper for visual development of a latent electrostatic irnagecomprising the steps of forming a latent electrostatic image on a copysheet formed of a conductive base sheet, said base sheet having a thincontinuous conductive barrier coating on each surface comprising aresinous barrier material which is a barrier to the penetration ofliquid developer and a comductor material selected from the groupconsisting of a polymeric quaternary ammonium halide selected from thegroup consisting of polydialkyl divinyl ammonium halides and polydialkyldiallyl ammonium halides and an ammonium salt of an alkyl arylsulfonate, and a second coating on one surface, said second coatingcomprising a material adapted to receive an electrostatic image andwetting the copy sheet with the developer liquid whereby the latentelectrostatic image becomes visually developed without development ofexcessive color in the base sheet.

13. The process as defined in claim 12 wherein said barrier material ispolyvinyl alcohol.

14. The process as defined in claim 12 wherein said conductor materialis polydimethyl diallyl ammonium chloride.

15. The process as defined in claim 12 wherein the conductor material isan ammonium salt of an alkyl aryl sulfonate in which the aryl group isselected from a group consisting of a benzene group and a naphthalenegroup and contains one or more alkyl groups having 1-20 carbon atoms.

16. The process as defined in claim 12 wherein coating contains 5-50percent by weight of said insulating material and l-75 percent by weightof said conductor material.

17. The process as defined in claim 12 wherein said conductive barriercoating includes vinyl acetate.

18. The process as defined in claim 17 wherein said vinyl acetate ispresent in an amount up to 40 percent by weight of said coating.

19. The process as defined in claim 12 wherein said coating includes ahydrate ammonium silicate.

20. The process as defined in claim 19 wherein said ammonium silicate ispresent in an amount within the range of -40 percent by weight of saidcoating.

21. The process as defined in claim 12 wherein said coating is presentin a dry coating weight of 2-14 pounds per 3,000

qu rqf s f sur e 22. The process as definedin clairn 12 wherein saidsecond coating is adapted to receive an electrostatic image and isselcte? from the groupconsistin'g ofahigh insulating materi al and aphotoconductive material. v

23. An electrophotographic reproduction sheet for development of alatent electrostatic image by a liquid developer comprising a conductivebase sheet having a thin continuous conductive barrier coating on eachside thereof, said coating comprising polyvinyl alcohol, a conductormaterial selected from the group consisting of a polymeric quaternaryammonium halide selected from the group consisting of polydialkyldivinyl ammonium halides and polydialkyl diallyl ammonium halides and anammonium salt of an alkyl aryl sulfonate, vinyl acetate and a hydratedammonium silicate, and a second coating on one side of the said basesheet, said second coating comprising a material adapted to receive anelectrostatic image.

2. A reproduction sheet as defined in claim 1 wherein said barriermaterial is polyvinyl alcohol.
 3. A reproduction sheet as defined inclaim 1 wherein said conductor material is polydimethyl diallyl ammoniumchloride.
 4. A reproduction sheet as defined in claim 1 wherein theconductor material is an ammonium salt of an alkyl aryl sulfonate inwhich the aryl group is selected from a group consisting of a benzenegroup and a naphthalene group and contains one or more alkyl groupshaving 1-20 carbon atoms.
 5. A reproduction sheet as defined in claim 1wherein coating contains 5-50 percent by weight of said barrier materialand 1-75 percent by weight of said conductor material.
 6. A reproductionsheet as defined in claim 1 wherein said barrier coating includes vinylacetate.
 7. A reproduction sheet as defined in claim 6 wherein saidvinyl acetate is present in an amount up to 40 percent by weight of saidcoating.
 8. A reproduction sheet as defined in claim 1 wherein saidbarrier coating includes a hydrated ammonium silicate.
 9. A reproductionsheet as defined in claim 8 wherein said ammonium silicate is present inan amount within the range of 15-40 percent by weight of said coating.10. A reproduction sheet as defined in claim 1 wherein said barriercoating is present in a dry coating weight of 2- 14 pounds per 3,000square feet of surface area.
 11. A reproduction sheet as defined inclaim 1 wherein said material for receiving the electrostatic image isselected from the group consisting of a high insulating material and aphotoconductive material.
 12. An electrostatic copy process in which useis made of a liquid developer for visual development of a latentelectrostatic image comprising the steps of formIng a latentelectrostatic image on a copy sheet formed of a conductive base sheet,said base sheet having a thin continuous conductive barrier coating oneach surface comprising a resinous barrier material which is a barrierto the penetration of liquid developer and a comductor material selectedfrom the group consisting of a polymeric quaternary ammonium halideselected from the group consisting of polydialkyl divinyl ammoniumhalides and polydialkyl diallyl ammonium halides and an ammonium salt ofan alkyl aryl sulfonate, and a second coating on one surface, saidsecond coating comprising a material adapted to receive an electrostaticimage and wetting the copy sheet with the developer liquid whereby thelatent electrostatic image becomes visually developed withoutdevelopment of excessive color in the base sheet.
 13. The process asdefined in claim 12 wherein said barrier material is polyvinyl alcohol.14. The process as defined in claim 12 wherein said conductor materialis polydimethyl diallyl ammonium chloride.
 15. The process as defined inclaim 12 wherein the conductor material is an ammonium salt of an alkylaryl sulfonate in which the aryl group is selected from a groupconsisting of a benzene group and a naphthalene group and contains oneor more alkyl groups having 1-20 carbon atoms.
 16. The process asdefined in claim 12 wherein coating contains 5-50 percent by weight ofsaid insulating material and 1-75 percent by weight of said conductormaterial.
 17. The process as defined in claim 12 wherein said conductivebarrier coating includes vinyl acetate.
 18. The process as defined inclaim 17 wherein said vinyl acetate is present in an amount up to 40percent by weight of said coating.
 19. The process as defined in claim12 wherein said coating includes a hydrate ammonium silicate.
 20. Theprocess as defined in claim 19 wherein said ammonium silicate is presentin an amount within the range of 15-40 percent by weight of saidcoating.
 21. The process as defined in claim 12 wherein said coating ispresent in a dry coating weight of 2-14 pounds per 3,000 square feet ofsurface area.
 22. The process as defined in claim 12 wherein said secondcoating is adapted to receive an electrostatic image and is selectedfrom the group consisting of a high insulating material and aphotoconductive material.
 23. An electrophotographic reproduction sheetfor development of a latent electrostatic image by a liquid developercomprising a conductive base sheet having a thin continuous conductivebarrier coating on each side thereof, said coating comprising polyvinylalcohol, a conductor material selected from the group consisting of apolymeric quaternary ammonium halide selected from the group consistingof polydialkyl divinyl ammonium halides and polydialkyl diallyl ammoniumhalides and an ammonium salt of an alkyl aryl sulfonate, vinyl acetateand a hydrated ammonium silicate, and a second coating on one side ofthe said base sheet, said second coating comprising a material adaptedto receive an electrostatic image.